YOSEMITE NATIONAL PARK — The Civil War was raging. Hundreds of thousands of Americans were dead.

But 150 years ago, President Abraham Lincoln found time to sign a two-paragraph bill that changed America’s landscape forever. Inspired by the early photographs of Carleton Watkins and paintings by Albert Bierstadt, the measure set aside the granite cliffs and magnificent waterfalls of California’s Yosemite Valley — as well as the ancient sequoia trees of the Mariposa Grove, 35 miles to south — “for public use, resort, and recreation … inalienable for all time.”

On Monday, park officials and political leaders will commemorate Lincoln’s June 30, 1864, signing of the Yosemite Grant Act, viewed by many as the birth of America’s national park system. And in an event that will reshape the iconic park for generations, construction crews plan to break ground the same day on a $36 million project to remove the noise, clutter and cars from Mariposa Grove.

“The first thing you see now is the gift shop, and the first thing you hear is a generator,” said Sue Beatty, a Yosemite biologist working on the sequoia project. “We want it to be a more reverential experience, and less commercial. More like it was in 1864.”

The 550-acre grove, home to some of the world’s largest living species, should be a place for reflection and awe, she said.

More than a century of tourism, however, has brought pavement and traffic jams. Asphalt parking lots and poorly designed hiking trails are compacting the roots of the trees, some more than 2,000 years old, limiting water flow and making it nearly impossible in many areas for new seeds to grow.

The park plans to remove Mariposa Grove’s 113-space parking lot and replace it with a new lot two miles away at the park’s south entrance near Wawona, with room for 260 cars.

Although disabled visitors still will be able to drive to the grove, starting in August 2016 all other visitors will ride shuttle buses that come and go every 10 minutes from the new lot. The gift shop will be removed. Old pit toilets will be replaced with modern restrooms; new trails and signs will go in. The tourist tram, ridden by nearly 100,000 people a year, will be discontinued.

“Sequoia groves are cathedrals. Providing a quieter, more relaxed experience in Mariposa Grove — no parking lots, no tram tours — will be much less chaotic,” said Mike Tollefson, president of the Yosemite Conservancy, a San Francisco nonprofit group that is donating $20 million to the project.

“Yosemite is a place to turn off your cellphone,” he said. “It’s a place where you aren’t in a hurry, where there’s not noise and you can contemplate nature.”

When Lincoln first set aside Yosemite Valley and Mariposa Grove for preservation, he deeded them to California. But over time they suffered — a large hog pen and hay-baling area were set up in Yosemite Valley, for example — and conservationist John Muir successfully urged Congress to establish a national park made up of the high country and surrounding lands in 1890. Then, in 1906, President Teddy Roosevelt incorporated the valley and grove into the new national park.

Lincoln’s act came at a time when the federal government was giving away millions of acres of the West for railroads, homesteads, logging, grazing and mining.

“The idea of preserving wilderness instead of exploiting it was very foreign to the American psyche in the 19th century,” said Miles Standish, a retired Santa Cruz state park ranger who dresses up as Galen Clark, Yosemite’s first ranger, in historic programs. “Today we accept it. But then it was a radical idea.”

Also unheard of at the time was the concept of preserving America’s most scenic lands not just for the wealthy, but for everyone.

“It was an incredible moment,” said Dayton Duncan, who wrote and co-produced “The National Parks: America’s Best Idea” in 2009 with filmmaker Ken Burns on PBS. “This was basically the Declaration of Independence writ onto the landscape. It was an expression of equality and the pursuit of happiness.”

During the planning of the Mariposa Grove restoration, most people testified in support of the plan. But some still chafe at the loss of the tram.

“I want what’s best for the trees. But we have older people and kids who are 2 years old,” said Aaron Vandenack, a concession worker from Wawona, as he helped tourists get aboard the tram for a $26 ride. “The upper grove is going to be off limits to a lot of people if there’s no tram.”

But Tollefson, a former superintendent of Yosemite, noted that 90 percent of the 1 million people who visit the grove now do not ride the tram. People with limited mobility, he said, will be able to walk on a new half-mile boardwalk in a meadow to see the huge trees.

On a recent Friday, most visitors said they didn’t mind losing the tram and parking lot.

“I don’t think the park should be managed based on what is most convenient for people, but what is best for nature,” said Olivier Caro, a San Mateo schoolteacher visiting with his son. “I trust the park rangers. They know the area.”

Monday’s groundbreaking ceremony at the Mariposa Grove will be open to the public beginning at 10 a.m. A fair with booths, guided walks and speeches marking the park’s 150th anniversary will run from 11 a.m. to 3:30 p.m. at the Yosemite Valley Visitor Center.

Stanford University is hosting a free exhibition of Carleton Watkins’ 19th century photos of Yosemite at the Cantor Arts Center, open Wednesday-Sunday 11 a.m.-5 p.m., and Thursday until 8 p.m. For more information, call 650-723-4177 or go to http://museum.stanford.edu.

Paul Rogers has covered a wide range of issues for The Mercury News since 1989, including water, oceans, energy, logging, parks, endangered species, toxics and climate change. He also works as managing editor of the Science team at KQED, the PBS and NPR station in San Francisco, and has taught science writing at UC Berkeley and UC Santa Cruz.

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